1. Field
The following description relates to an apparatus and method for originating a call by substitute communication network when originating a call in a communication network is barred.
2. Discussions of Background
Long Term Evolution (LTE) is a term named after a next-generation communication technology evolving from the third-generation (3G) mobile communication. LTE is also referred to as 3.9 generation (3.9G) mobile communication as a technology positioned between the 3G mobile communication represented by a wideband code division multiple access (WCDMA), a code division multiple access (CDMA) 2000, etc. and the fourth-generation (4G) mobile communication, and is one of leading candidates for the 4G mobile communication technology.
Since an LTE network system is a data-dedicated network configured by an all-IP network, the LTE network system supports only a packet switching (PS) network but does not support a voice call that is transmittable through a circuit switching (CS) network. Thus, in order to support a voice service in the LTE network system, additional technology is necessary. The Voice over Long Term Evolution (VoLTE), acquired by profiling circuit switched fall back (CSFB) and IP multimedia subsystem (IMS), is currently a popular representative technology.
The VoLTE serves not only a data call but also a voice call through a PS network. When a considerably high load is applied to an LTE network base station to process large amounts of data calls, the LTE network base station additionally needs to process voice calls. Accordingly, in a region where many users are densely populated, due to overload of the base station, users may not be able to use not only a data call but also a voice call. For example, in a region where many users are densely populated, such as a football field or a concert hall, because one base station needs to process a large amount of data transmitted from a large number of portable terminals, calling services of some portable terminals may be barred. In such a case, some users may not be able to use any call originating services of their portable terminals.
The process in which originated calls are barred will be described more specifically with reference to FIG. 1.
In operation S10, a portable terminal is registered in an LTE network. After the portable terminal performs a cell search to search for a communicable base station, the portable terminal and the cell are synchronized with each other. After the synchronization, the portable terminal acquires a physical layer identity (ID) of the cell and searches for cell frame timing, whereby the portable terminal may be registered in the LTE network.
Thereafter, in operation S11, the portable terminal receives system information block 2 (SIB2) messages at regular time intervals. The SIB2 message includes cell information that is needed for a portable terminal to appropriately operate within a corresponding cell and necessary information for barring the call of a portable terminal belonging to the cell.
In operation S12, if an originating call barring message is present within the SIB2 message, the portable terminal stores the originating call barring message. An originating call barring message includes an ac-BarringInfo message, and the ac-BarringInfo message includes ac-BarringForEmergency, ac-BarringForMO-Signalling, and ac-BarringForMO-Data Information Element (IE). In addition, ac-BarringForMO-Signalling and ac-BarringForMO-Data IE include ac-BarringConfig IE, and ac-BarringConfig IE includes sub-IEs ac-BarringFactor, ac-BarringTime, and ac-BarringForSpecialAC. Here, ac-BarringFactor has numbers (for example, 0, 0.05, 0.1, and 0.15 to 0.95) within a range equal to or larger than zero and smaller than one, [0,1). In addition, ac-BarringTime has a value between 4 seconds to 512 seconds. When the portable terminal receives the SIB2 message, all the IE values within ac-BarringInfo are stored.
Thereafter, in operation S13, the portable terminal receives a request for originating a call from a user input. For example, the user inputs a text to the portable terminal and requests the transmission for sending a message. The portable terminal determines whether a VoLTE connection may be made to a corresponding cell based on the user's request for originating a call.
Specifically, in operation S14, the portable terminal checks whether the ac-BarringForMO-Data IE is present within the ac-BarringInfo message. When the ac-BarringForMO-Data IE is not present, in operation S18 the portable terminal tries to originate a call using the LTE cell.
However, in operation S15, if the ac-BarringForMO-Data IE is present, an access classes (AC) value stored in a USIM of the portable terminal is checked to determine whether the AC value has a value in the range of 11 to 15. If the AC value has a value in the range of 11 to 15, in operation S18 the portable terminal tries to originate a call using the LTE cell.
On the other hand, in operation S16, if the AC value has a value in the range of 0 to 9, the portable terminal checks if the difference between a random value and the ac-BarringFactor value is greater than zero. The random value represents a random number that is generated in the range of 0 to 1 at the same probability and is internally generated by the portable terminal.
If the difference in operation S16 is less than zero, in operation S18 the portable terminal tries to originate a call in a corresponding LTE cell. On the other hand, in operation S17 if the difference in S16 is greater than zero, originating a call from the portable terminal is barred in the corresponding cell. The barring of the originating call continues for a predetermined time at a specific probability until the ac-BarringForMO-Data IE is no longer received through the SIB2 message.
As described above, if a large number of users are densely populated within a specific cell, originating a call from a portable terminal by an arbitrary user within the cell may be barred. Since originating a call includes not only a data call but also a voice call, an arbitrary user within a cell where originating a call is barred may not use most of the data communication services.